COMMON WEAKNESS ENUMERATIONIncomplete

CWE-128

Wrap-around Error

Wrap around errors occur whenever a value is incremented past the maximum value for its type and therefore "wraps around" to a very small, negative, or undefined value.

Abstraction

Base

Structure

Simple

Likelihood of Exploit

Medium

Understand the problem

What is the problem?

Wrap around errors occur whenever a value is incremented past the maximum value for its type and therefore "wraps around" to a very small, negative, or undefined value.

Root cause

How and when does the problem arise?

Lifecycle phase

Implementation

Due to how addition is performed by computers, if a primitive is incremented past the maximum value possible for its storage space, the system will not recognize this, and therefore increment each bit as if it still had extra space. Because of how negative numbers are represented in binary, primitives interpreted as signed may "wrap" to very large negative values.

Risk

What does successful exploitation lead to?

DoS: Crash, Exit, or RestartDoS: Resource Consumption (CPU)DoS: Resource Consumption (Memory)DoS: Instability

Affected security scopes: Availability

This weakness will generally lead to undefined behavior and therefore crashes. In the case of overflows involving loop index variables, the likelihood of infinite loops is also high.
Modify Memory

Affected security scopes: Integrity

If the value in question is important to data (as opposed to flow), simple data corruption has occurred. Also, if the wrap around results in other conditions such as buffer overflows, further memory corruption may occur.
Execute Unauthorized Code or CommandsBypass Protection Mechanism

Affected security scopes: Confidentiality, Availability, Access Control

This weakness can sometimes trigger buffer overflows which can be used to execute arbitrary code. This is usually outside the scope of a program's implicit security policy.

Defence

How is it prevented and fixed?

All phases

General mitigation and defence approach

Detail
Requirements specification: The choice could be made to use a language that is not susceptible to these issues.

Architecture and Design

Architecture and design approach

Detail
Provide clear upper and lower bounds on the scale of any protocols designed.

Implementation

Implementation-phase defence

Detail
Perform validation on all incremented variables to ensure that they remain within reasonable bounds.

Verification

How is it detected?

Automated Static Analysis

High
Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then searching for potentially-vulnerable patterns that connect "sources" (origins of input) with "sinks" (destinations where the data interacts with external components, a lower layer such as the OS, etc.)